• Proceedings of the KAIS Fall Conference
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• 2006.05a
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• pp.585-586
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• 2006

본 연구에서는 고도처리를 위한 BNR 공정에 사용되는 MBR (Membrane Bioreactor)의 막 오염(membrane fouling)을 저감시키기 위해 분리막을 침지시킨 침전조를 상하로 나누어 상부는 폭기조로, 하부는 침전조의 역할을 수행하게 하는 새로운 형태의 막분리 침전조 (aerated settler)의 성능을 평가 하였다. 막분리 침전조는 상하로 구분하기 위해서 baffle을 설치하였다. 파일럿 규모 ($Q=50m^3/d$)의 MBR 공정은 실제 오수를 유입수로 사용하였으며 약 6개월간 운전하였다. 탈질을 위하여 막분리 침전조 하부에서 무산소조로 반송되는 반송수의 DO를 크게 줄어들게 함으로써 무산조에서의 탈질효율이 증가되었다. 처리수의 총 TN 제거율은 75%이었다. 또한 막분리침전조 상 하부의 MLSS 농도 차에 의해 상부에 침지된 막 모듈은 기존의 MBR 공정보다 막 오염 저감 효과가 있어서 세정주기가 증가하였다. 운전 개시 후 4개월째 되는 시점에 TMP가 40cmHg에 도달하여 1회 화학적 약품세정만이 필요하였다.

• Korean Journal of Environmental Biology
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• v.25 no.2
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• pp.81-87
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• 2007

The removal of Microcystis aeruginosa and Chlorella zofingiensis by ceramic powder was investigated on the basis of both the particle size (under 0.05, 0.1, 1 mm) and the dosage (0.1, 1, $10\;g\;L^{-1}$) of the ceramic powder. The removal efficiencies of M. aeruginosa and C. zofingiensis were highest with a particle size of 0.05 mm and a dosage of $1\;g\;L^{-1}$ of the ceramic powder in laboratory experiment. $chlorophyll-{\alpha}$ concentrations decreased in both field and enclosure samples with a particle size of 0.05 mm and a dosage of $1\;g\;L^{-1}$ of ceramic powder, resulting in the removal efficiencies of 67 and 69%, respectively. Consequently, it was concluded that the ceramic powder could be used to control algal bloom by removing $chlorophyll-{\alpha}$ in eutrophic waters.

• The KSFM Journal of Fluid Machinery
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• v.7 no.6 s.27
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• pp.55-61
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• 2004

A numerical procedure for optimizing the shape of three-dimensional sedimentation tank is presented to maximize its sedimentation efficiency. The response surface based optimization is used as an optimization technique with Reynolds-averaged Navier-Stokes analysis for multi-phase flow. Standard $k-{\epsilon}$ model is used as a turbulence closure. Three design variables such as, tank height to center feed wall diameter ratio, blockage ratio of center feed wall and angle of distributor are chosen as design variables. Sedimentation efficiency is defined as an objective function. Full-factorial method is used to determine the training points as a means of design of experiment. Sensitivity of each design variable on the objective function has been evaluated. And, optimal values of the design variables have been obtained.

• Journal of the Mineralogical Society of Korea
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• v.27 no.2
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• pp.97-105
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• 2014

Artificial precipitation ponds, consisting of three steps of oxidation pond, successive alkalinity producing system (SAPS) and swamp, were constructed for the treatment of the acid mine drainage from the Iwal coal mine. The efficacies of the passive treatment system in terms of neutralization of mine water and removal of dissolved ions were evaluated by the chemical analyses of the water samples. Mine water in the mine adits was acidic, showing the pH value of 2.28-2.42 but the value increased rapidly to 6.17-6.53 in the Oxidation pond. The purification efficiencies for the removal of Al and Fe were 100%, whereas those of $SO_4$, Mg, Ca, and Mn were relatively low of 50%, 40%, 24%, and 59%, respectively. These results indicate a need for application of additional remediation techniques in the passive treatment systems. The precipitates that formed at the bottom of the mine water channels were mainly schwertmannite ($Fe_8O_8(OH)_6SO_4$) and those in the leachate water were 2-line ferrihydrite ($Fe_2O_3{cdot}0.5H_2O$).

• Journal of the Korean GEO-environmental Society
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• v.11 no.6
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• pp.69-75
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• 2010

Total suspendid solid (TSS) of non point source pollutants in construction site are in higher concentration than others (BOD, COD etc). Also, the TSS concentration is very sensitive to the rainfall intensity in early stage of construction. There are two methods for treatment of non point source pollutants, which are temporary treatment facility and filtering one. But they have disadvantages. Temporary facility system has very low efficiency and filtering system consumes high energy and takes up large footprint. This study shows how prefabricated flocculation/coagulation system is developped to cover the above weakness and evaluation of the system performance in construction site. The prefabricated flocculation/coagulation system has very high treatment efficiency comparing with temporary and filtering system and takes small footprint. Therefore, it expects that the system leads to prevention of pollution near construction site and reduction of public grievance. Proper coagulant dosage and sludge circulation facility application, controlling the height of sludge interfacial are necessary to maximize the system efficiency.

• Microbiology and Biotechnology Letters
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• v.42 no.1
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• pp.25-31
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• 2014

Fractional precipitation is a simple method for purifying (+)-dihydromyricetin extracted from biomass. However, the fractional precipitation process has been inherently problematic due to the lengthy precipitation time that is required. The fractional precipitation time was shortened and (+)-dihydromyricetin yield was improved by increasing the surface area per working volume (S/V) of the reacting solution through the addition of a cation exchange resin (Amberlite 200, Amberlite IR 120Na, Amberlite IR 120H, or Amberlite IRC 50). Most of the (+)-dihydromyricetin (>90%) could be obtained after about 16 h of fractional precipitation using Amberlite 200. Since high-purity (+)-dihydromyricetin can be obtained at a high yield and the precipitation time can be reduced by increasing the surface area available for precipitation, this improved method is expected to minimize solvent usage and the size and complexity of the high performance liquid chromatography operation required for (+)-dihydromyricetin purification.

• KSBB Journal
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• v.21 no.3
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• pp.199-203
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• 2006

Precipitation and reactive distillation were employed to recover lactic acid from fermentation broth. Lime was initially added to fermentation broth in order to convert soluble lactic acid to an insoluble calcium lactate form. Drowning-out crystallization was used to decrease the solubility of calcium lactate by adding ethanol as a co-precipitant. In the ideal solution of organic acids as well as fermentation broth, precipitation experiments were performed with varying amounts of ethanol. Precipitation process was followed by reactive distillation. Carboxylate salts formed in the previous precipitation process were mixed with carbon dioxide and triethylamine to precipitate as calcium carbonate. The remaining liquid was distilled for 1 hr at different temperatures. Triethylamine and water were recovered from the top of the distiller, while organic acids, inducing lactic acid as a main component remained in feeding bottle. The yield of recovered lactic acid was 67.5% with the purity of 99.7%.

• Journal of the Korean Geotechnical Society
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• v.39 no.8
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• pp.7-16
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• 2023

This study aimed to evaluate the sulfate removal capacity of the enzyme-induced carbonate precipitation (EICP) technique through the chemical precipitation of sulfate with calcium ions. The optimal EICP recipe was obtained to retain the excess calcium cations in the solution for the generation of a sufficient amount of calcium carbonate (CaCO₃) mineral. The effect of gypsum precipitation on the EICP-treated sand specimen was investigated by measuring the shear wave velocity and by visual inspection via scanning electron microscopy. The EICP solution using soybean crude urease, as an alternative to laboratory-grade purified urease, exhibited a lower sulfate removal efficiency at a similar CaCO₃ production rate compared with the optimal EICP recipe because of soybean impurities.

• Korean Journal of Soil Science and Fertilizer
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• v.26 no.1
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• pp.37-42
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• 1993

Influences of metal concentration, pH and temperature on metal-ligand precipitate formation were investigated, as a part of projects for removing heavy metals from aqueous solution employing the principles in metal-ligand complexation. Aqueous solutions of HA or FA were reacted with those of heavy metals with 1:1 ratio. Efficiency of humic (HA) or fulvic acid (FA) on removing metals was evaluated by separating the precipitates from soltuions with the filtering method. When HA was a counter ligand, there existed three ranges of metal concentrations affecting precipitation : precipitate fromation was not available, was reached to the maximum, and afterwards was decreased again. The concentration ratios of metal to HA for initiating complexation were dependent upon kinds of metal and concentrations of ligand. Amount of Pb to form maximum precipitates per unit mg of HA was 1.3 times higher than that of Cu. When FA was a counter ligand, concentrations of metal-FA precipitates were increased proportionally with the treated metal concentrations. Efficiency of FA fro removing Pb was nearly 100%, but it was ranged from 12 to 19% for Cu, depending on FA concentration. pH exerted a considerable effect on complexation between Pb and FA, showing precipitates were increased six times at most per unit increase of pH. Ranges of pH increasing significantly the mounts of precipitates were coincied with pH jump ranges of the titration curve of organic ligands. As increasing temperature from 15 to $55^{\circ}C$, increases of FA-Cu precipitates were doubled, but those of FA-Pb were accounted for only 6%, However, HA-metal complexation was not affected by temperature.

• Economic and Environmental Geology
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• v.42 no.5
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• pp.445-455
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• 2009

Microbiological sulfate reduction is the transformation of sulfate to sulfide catalyzed by the activity of sulfate-reducing bacteria using sulfate as an electron acceptor. Low solubility of metal sulfides leads to precipitation of the sulfides in solution. The effects of microbiological sulfate reduction on in-situ precipitation of arsenic and copper were investigated for the heavy metal-contaminated soil around the Songcheon Au-Ag mine site. Total concentrations of As, Cu, and Pb were 1,311 mg/kg, 146 mg/kg, and 294 mg/kg, respectively, after aqua regia digestion. In batch-type experiments, indigenous sulfate-reducing bacteria rapidly decreased sulfate concentration and redox potential and led to substantial removal of dissolved As and Cu from solution. Optimal concentrations of carbon source and sulfate for effective microbial sulfate reduction were 0.2~0.5% (w/v) and 100~200 mg/L, respectively. More than 98% of injected As and Cu were removed in the effluents from both microbial and chemical columns designed for metal sulfides to be precipitated. However, after the injection of oxygen-rich solution, the microbial column showed the enhanced long-term stability of in-situ precipitated metals when compared with the chemical column which showed immediate increase in dissolved As and Cu due to oxidative dissolution of the sulfides. Black precipitates formed in the microbial column during the experiments and were identified as iron sulfide and copper sulfide. Arsenic was observed to be adsorbed on surface of iron sulfide precipitate.